Hi Dave,
Yes I understand you want the SDK.
There is no free download for the SDK.
Download the ASE developer edition, it comes with the SDK inside.
When downloaded you can run the ASE installer.
From there you select 'custom installation'
Once selected you will see the list of products.
Select all the client tools you want. (ie ctlib, odbc, ado.net, etc).
Regards,
Ryan